Recently, I was watching the new PBS show called Breakthrough: The Ideas That Changed The World, narrated by sir Patrick Stewart. This new PBS series is really interesting and worth watching, as it has episodes on topics such as telescopes, smartphones, and rockets. One of the earliest scenes in the rockets episode has an animation of a launch of a spacecraft and the comment is made that humanity is developing rockets that will take humans to deep space for the first time in nearly 50 years.

This made me think and person who I was watching with ask, “Is the moon really considered deep space?” and what does this term really mean?!?

Some say that anything beyond the Earths atmosphere is deep space, whereas others use the term to reference anything beyond the solar system.

More formal definitions include the International Telecommunication Union definition of “deep space” starts at a distance of 2 million km from the Earth’s surface. The NASA Deep Space Network has variously used criteria of 16,000 to 32,000 km from Earth. 

What this means is that some definitions have the moon as a deep space object, whereas, the moon is not far enough away to qualify. The moon lies 384,400 km from Earth, which is not far enough away to qualify for the ITU definition. However, this means for the DSN, the moon does qualify. Another example is the planet Mars is 54.6 million km away from Earth, which does qualify.

This lack of consistency is something that can confuse those using the terminology, which means that a widely accepted standardization might be beneficial.

What does the term mean to you? How do you use it? Let us know!